High-End Bike Buying

Choose Your Weapon

Your next high - end bike hunt could present you with a perplexing (& wonderful) conundrum: ultralight or aero?

matt phillips

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When you walk into a shop to buy a race-level road bike, the process might seem more complicated than ever--and not only because you have to decipher all the claims that "our carbon is better than theirs," or "this new bottom-bracket design is best," or "trust us, electric shifting is revolutionary." Choosing a new bike can be confounding because a growing number of manufacturers are producing two distinct frames that can each be called the company's fastest.

One style of bike has the telltale, angular shaping of a wind cheater; the other has the delicate curves of a lightweight that flouts gravity. And this time the hype is true: Each one really might be the fastest bike you've ever ridden--it depends on the kind of speed you crave.

FEATHER VS. KNIFE Of the many ways to evaluate a frame's potential performance, lightness is the easiest to understand. You can simply pick up two frames and feel a weight difference (which might explain, in part, why so many cyclists obsess over every gram). Everyone intrinsically understands that we can move a lighter object more easily than a heavier object, so paying more for a lighter bike makes sense.

This is backed up by more thorough study. Unlike some commonsense ideas that turn out to be false, weight truly does matter, especially on climbs. Reliable calculators, easily found on the Internet, show how much faster a lighter bike is on an ascent. For example, on a 6-mile hill with a constant 8 percent grade and a rider who puts out a consistent 250 watts, reducing weight by 250 grams will result in a time savings of more than seven seconds. (But remember that these calculations are based on unrealistically constant parameters-- in the real world, wind changes speed and direction, the grade varies, your friends draft or attack.) To smaller degrees, a lighter bike also helps when you're quickly accelerating, such as in an attack, or changing speeds frequently to adjust for grade or your companions. By contrast, the effect of a bike's weight can be surprisingly negligible on a flat road at a constant effort.

Aerodynamic drag has significantly more impact on you--up to 90 percent of the resistance you're working against when riding a bike. Because drag is every rider's biggest foe, some companies put monumental effort into making bikes that slice through the air. But the payoff isn't always proportionate to the effort: Unlike the instant feedback a potential buyer gets by lifting a bike in a showroom, the benefit of aero improvements can be difficult to grasp. More important, so much drag comes from the rider that the bike is responsible only for about 10 percent of that 90 percent of resistance. Even so, improvements to frame aerodynamics matter. Cervelo cofounder Gerard Vrooman says that his aero-shaped S3 frame lets the average rider gain 10 meters per kilometer compared with the R3-SL , which is 200 grams lighter (again, more numbers based on controlled situations, and which may not translate to your Tuesday-evening loop).

So to recap: Improvements to either aerodynamics or weight result in additional speed. The difference is in the type of speed. In general, the aero bike is faster on flats and longer, sustained efforts, and the lighter bike is faster on climbs and in pack situations (with lots of drafting that minimizes aerodynamic advantages) that involve repeated, sharp accelerations.